Washington, Nov 16 (IANS) As President Barack Obama prepares to announce his new strategy for Afghanistan, his administration is stepping up pressure on Pakistan to expand and reorient its fight against the Taliban and Al Qaeda, the New York Times reported Monday.

As Obama travelled to Asia, his national security adviser, Gen. James L. Jones, was quietly sent to Islamabad to warn that failing to do so would undercut the new strategy and troop increase for Afghanistan, the influential US daily said citing unnamed American officials.

His message, the daily cited officials as saying, was that the new American strategy would work only if Pakistan broadened its fight beyond the militants attacking its cities and security forces and went after the groups that use havens in Pakistan for plotting and carrying out attacks against American troops in Afghanistan, as well as support networks for Al Qaeda.

While Afghanistan has dominated the public discussion of Obama's strategy, which officials say could be announced as early as this week, Pakistan is returning to centre stage in administration planning, the Times said.

The daily said General Jones praised the Pakistani operation in South Waziristan but urged Pakistani officials to combat extremists who fled to North Waziristan.

General Jones also delivered a letter from Obama to Pakistan's president, Asif Ali Zardari, in which Obama said he expected Zardari to rally the nation's political and national security institutions in a united campaign against extremists threatening Pakistan and Afghanistan, it said citing an unnamed official briefed on the conversations.

In his letter to Zardari, Obama offered a range of new incentives to the Pakistanis for their cooperation, including enhanced intelligence sharing and military cooperation, the Times said citing officials.

For their part, Pakistani officials have told the Americans that they harbour two deep fears about Obama's new strategy: that the US will add too many troops on the Afghan side of the border, and that the American effort will end too soon, it said.

Their first concern, described by officials on both sides of the recent discussions, the Times said, is that if Obama commits an additional 30,000 or more troops, it will inevitably push more Taliban fighters across the border into Pakistani territory and complicate the South Waziristan offensive.